1. Field of the Invention
This invention relates to heat dissipation in electrical circuits. Particularly, this invention relates heat dissipation in electrical circuits for space applications.
2. Description of the Related Art
In electrical circuits for space applications and generally, heat dissipation requirements tend to increase with more capable electronics. Conventional designs commonly employ heat-sinks mechanically fastened to the die, i.e. bonded to the die and local area of a printed wiring board (PWB), or vias under an ASIC and removed from the die heat-source. However, these designs commonly result in multiple thermal choke points. Thus, improving performance with conventional techniques requires updating design at multiple thermal interfaces. High performance thermal bonds are required, as well as a highly conductive but mechanically compliant heat-sink material. As the power dissipation increases much more area is required to transfer heat away.
Although circuit cooling has been developed using non-conductive liquid, such cooling systems require special architechtures and complex components which designed integrally with the circuit they are intended to cool. For example, microchannels for conducting cooling fluid have been developed which flow under capilary pressure. In addition, other self-contained fluid cooling systems for electronic circuits have been developed for personal computers. Some other circuit cooling systems may employ heat pipes. However, none of the developed systems lend themselves to being easily integrated with an existing chip type or retrofitted to an existing circuit design.
U.S. Pat. No. 6,687,124, by Ostby, issued Feb. 3, 2004, discloses an apparatus for cooling electronic components disposed in a sealed container in a phase change electronic cooling system including a hood disposed in the container adjacent the electronic components. The electronic components and the hood are immersed in a nonconductive liquid that partially fills the container when the container is in a predetermined location relative to the ground. The apparatus also includes at least one cooling tube having one end connected to the hood and an opposite end disposed adjacent a portion of the electronic components whereby during operation the electronic components transfer heat to the liquid, causing the liquid below the hood to vaporize forming bubbles, the bubbles traveling through the at least one tube and carrying an entrained portion of the liquid to said opposite end. When the container is oriented to expose the portion of the electronic components above the liquid level, the bubbles and the entrained liquid exit the opposite end of the at least one tube onto the exposed portion of the electronic components to cool the exposed portion of the electronic components.
In space applications, the ability to effectively transfer excess heat to space has not kept pace with the demands of the higher power electronics being employed. For example, transferring approximately 20-50W of heat from a smaller than one inch square ASIC die with a minimal temperature rise would be highly desireable. Various space vehicles, e.g. communication satellites, typically employ a large number electrical circuits in the systems which operate them. Each of these circuits must include a proper thermal design to remove excess heat developed during the operation of the circuit.
In view of the foregoing, there is a need in the art for apparatuses and methods for efficiently dissipating heat developed in electrical circuits. In addition, there is a need for such apparatuses and methods to be readily integrated with existing chip types. There is also a need for such apparatuses and methods that can be easily retrofitted to an existing circuit design. There is further a need for such systems and apparatuses in space applications. Theses and other needs are met by the present invention as detailed hereafter.